US1835978A - Multiple closed circuit hydraulic system - Google Patents

Description

DeC- 8, 1931. H. ERNST ET AL l MULTIPLE CLOSED CIRCUIT HYDRAULIC SYSTEM.

Filed May 15, 1929 q). Ni,

wucmtow Patented Dee. 8`, 1931 'UNITED STATES PATENT OFFICE;

, HANS ERNST AND LESTER F. N'ENNINGER,

or CINCINNATI, oIII'o, assIeNoBs rro 'mm F OHIO Application l'ed lay 15,

This invention relates to hydraulic trans-` missions of that type which seeks to eEect a uniform rate of movement of ianlactuated member by delivering into an hydraulic motor, at a volumetrically constant rate, what may be termed pushing-oil.

Hydraulic systems ofl this nature, while .not limited thereto, are particularly advantageous when utilized to actuate a.- reciprocatory element of a machine tool, such, for example, as the work-table of a milling machine. The invention will therefore,.for convenience, be'described in connection with that particular type of machine tool. The work-table of a milling machine must, d for practical operation, be translated at various times in opposite directions and at rapid and slow rates, the rapid translation being employed quickly to position the work relative to the tool prior to a machining operation, and the slow translation beingv utilized to feed the 'work past the tool during the cutting. operation.

Present day milling machines are adapted to cut either with or against the feed, that is, the cutter may be so rotated that its action on the work imay tend to drag the work in the direction of the feed or it may be rotated in the opposite direction with respect to the movement of the work whereby the action of the cutter on the work tends to retard the movement of the table.

To give to the table its required movements and to insure a uniform rate of travel under the-.varying conditions, we have heretofore/ rovided an hydraulic system comprising a i h capacity low pressure pump adapted to e ect rapid traverse of the table, a relatively lower capacity high pressure pump adapted to force oil into the receiving end of the hydraulic motor to eiect slow feeding movements of the iston and the table connected therewith, an a third or booster pump of relatively high pressure and lower capacity connected to the exhaust end o fthe motor and adapted tov maintain a high back pressure therein. This system forms the sub- 'ect of our pending application, Serial Numbei' 362,414, filed May 11, 1.929.

In the system disclosed in said application MULTIPLE CLOSED CIRCUIT HYDRAULIC SYSTEM 192s. serial No. 363.280.

the amount of back'y pressure in the exhaust end of the motor is controlled by a high pressure relief valve through which a portion of the oil delivered by the" booster pump is exhau'sted.l

The present invention is an improvement over that set forth in our prior application, in that it embodies all of the advantages of the prior systemM and, in addition, provides a construction in which, during thejrapid traverse movement of the work-table, the booster pump is enabled to exhaust through a relatively low-pressure relief valve instead of the high' pressure relief valve above referred to, through which it exhausts during slow-feeding movements of the table. By reason of this constructionl and arrangement the powercloss during .rapid traverse movement of the" table will be substantially less' than in our prior system. A

In the annexed drawings, forming a part of this disclosure, Figure 1 is a diagrammatic view of our improvedhydraulic system, the

cont-rolling valves thereof being so set as to effect slow feeding movement of the actuated element to the left, the rate of feed being determined by the action of a variable delivery pumpconnected with the intake end of the hydraulic motor. Fig. 2 is a similar view with the valves set in. a different position, thereby -to effect a rapid traverse movement of the actuated element to the left.

Referring more specifically to the drawl ings, the improved hydraulic system-is disclosed as comprising a reservoir RJl adapted to contain a supply of actuatingfliquid, preferably oil; van hydraulic motor H, comprising a cylinder 1 and piston 2, and a plurality of pumps, valves and conduits, later to be described, connecting the ,reservoir and the motor. The motor is, of course, intended to -do work and this'may be'efected by having the piston 2 connected, as by a piston rod 3, with a reciprocatory element or table' 4.

For the purpose of this disclosure' the ele-l ment 4 may be considered, to be the worktable of a milling -machine inasmuch as'the features of this invention may 'be employed to advantage when embodied in that type of machine tool.

The pumps embodied in this system comi prise a low pressure high capacity pump RT, adapted tovefect rapid traverse movements of the reciprocatory table 4; a low capacity able source but preferably it is connected to f through conduit 6, port 7 in v alve L and `receive oil from the exhaust end of the hy draulic motor. moved at an desired uniform rate, the pump Z is preferably of the variable delivery type which, by means of adjustment, may be caused to deliver oil into theintake end of the motor at any desired.volumetrically uniform ratei-from zeropto the maximum capac.

ity of the pump.

Intermediate the pumps RT, B and Z and the hydraulic motor H, arg two valves, one,- L, which serves as `a'selector or main control valve and the other,-M, which serves asa supplemental or stop valve. The valve L is adapted to control the direction of lflow of oil to and from the motor H and to determine."

which of the .pumps RT or Z may be effective to actuate said motor. The valve M serves either'to jconnect the motor with the valve L, as shown in full' lines in the drawings, or to isolate the motor from the valve L and the pumps, as shown in dotted lines in Fig. ,1, therebyto trap theoil in the opposite ends of the motor when it -is desired to lock the table 4 against movement in either direction.

rIfhe construction and operation of the valves L and M are clearly shown and To enable the table to be variable delivery pump Z wherebyoil exhausted from the left end of the cylinder is forced into the right end thereof, making, in

effect, a substantially, closed circuit.

As previously stated, it is desirable that a high back pressure be maintained in the exhaust end of the motor H. This is effected by means of the high pressure booster pump vB which draws oil from the reservoirl R through conduit 16 and discharges it through conduit 18 which is connected with the-conduit 15 by means of the conduit 5, port 7, and conduits 6 and 17 The excess oil delivered by the pump B is returned tothe reservoir through a relief line 18 controlled by a high pressure relief valve 19, the setting of which determines the amount of back pressure on the exhaust end of the hydraulic motor.

In certain milling operations in which the action of the cutter on the work tends to move the work-table in the direction of feed, in

Y 19 be set to withstand a pressure up to 400 described in our application, Serial Number 220,721, filed September 15,-1927 and also in British Patent No. 297,104. Detailed illus# tration and description thereof,in this application, is therefore deemed unnecessary.

' Fig. 1` shows the valves set to effectv slow i feeding movement of the table 4 to the left. In this setting of the valves the rapid traverse pump RT is short circuited, drawing oil in throughconduit 5 and discharging it returning it to the pump through conduit 5.

i Thus i`n this setting of the valves the .rapid traverse pump has no effectupon the hydraulic motor. As shown in Fig. 1 the pump Z has its discharge port connected, by conduit 8, port 9 invalve L, conduit 10, through valve M, conduit 11 with the right end of the hydraulic motor H, thereby( injecting oil thereinto and causing movement of the piston 2 and table 4 to the left. Oil in the left end of the cylinderl is exhausted throughconduit 12,;'through valve M, conduit 13, port 14 in valveL, and conduit 15. Preferably the conduit l5 connects with the intake port offthe lbs. per square inch. It is therefore' obvious that the exhaust of any substantial amount of oil through that valve would result in the consumption of a substantial amount of power and likewise would result in the undesirable heatingyof the oil.'

In our applicati-n, Serial No. 362,414, abovereferrel to, we have disclosed a system in -which the amount of oil Yexhausted against high backpressure is materiallyless than in prior` systems. The'. present invention provides. a 'systeminLwhich the amount of oil 'order vto produce the required margin of exhausted against high back pressure is still further reducedhy. l Fig. 2 shows thevalve L set to effect rapid traversel movement of the table 4 to the left.

los l In thissetting, the pump Z is short circuited, l

thereby effecting a continuous `flow4 of oil through conduit 8, port 20, inithe valve L, and conduit 15. The v hi'gh' capacity rapid traverse'p'ump RT has its intake port connected by conduit 5;, port 21, in valve L, conduit22, through valve M, and conduit 23, with `the left or 4exhaust end of the hydraulic motor H. Thefdischarge port of the pump lRT is connected by conduit 6, port 24, in

valve L, conduit 25, through .valve M, and

said m or. Thus it will be seen that a large volume of oil will berapidly withdrawn from the left en'd of the cylinderl 1 and forced into the right end thereof, thereby'edecting a rapid movement of the piston 2 and t-able 4 to the left. During this rapid traverse -movement the constantly7 acting booster pump B is not required to discharge against the h igh back pressure of the valve 19 as it does during the'feeding movement. As will be perceived from an inspection `of Fig. 2, the pump B has'itsfdischarge port connected, as by means of conduit 18, with the intake 'side conduit;` 26 with the right or Vintake end of '1 suffice.

of the rapid traverse pump RT. The conduit 18 is also connected, by conduit 5, port 21, and auxiliary return conduit 27, with the reservoir R. The latter conduit is closed at its lower end by a low pressure relief v,alve"28. This valve serves merely to prevent the oil from draining freely to the reservoir, therefore a setting of this valve to produce a back pressure of pounds per square inch will ent'system 4during the rapid traverse movement the booster pump exhausts against a `substantially lower back pressure than it does in our prior system above referred to, and tlzherefore the power losses will be materially ess.

Although only two positions of the valve L have been shown and described it is to be understood that it may be shifted to two 20. other positions in which the system effects respectively rapid traverse and slow feed'to the right. Likewise the valve M may be shifted to the position shown vin dotted lines in Fig. 1 to isolate the hydraulic motor from all of the three pumps and to close the conduits 1 1 andl2 against exhaust. This traps oil in the opposite ends of the cylinder' and positively locks the pisto'n 2 and table 4 against movement in either direction.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations by retaining one or more of the features that,

from the standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this inven-v tion and, therefore, such adaptations 'should be, and are intended to be, comprehended 4 within the meaning and range of equivalency of the following claims;l i Having thus revealed this invention, we claini as new and desire to secure the following combinations nd elements, or equivalents thereof, by-Letters Patent of United States 1. Anl hydraulic system .combining a. motor; a reservoir; a high capacity pump adapted to deliver oil into said motor to effect relatively rapid actuation thereof; a second pump adapted to be connectedl with the intake side of said motor to deliver oilthereinto, thereby to effect relatively slow actuation thereof; a third pump, receiving oil from said reservoir, adapted, when the second pump is connected 'with the intake side of said motor to have its discharge port connected with the exhaust side of said motor thereby to maintain therein a pressure counter to the pres- 50, sure built up in the intake side thereof by said -second pump; a relatively high pressure relief line connected with said third pump and effective during actuation of saidvmotor by said second pump; and a relatively .low pressure relief line .connected with said third Thus it will be seen that in thepres-y pump and effective during rapid actuation of said motor by said first pump. c

2. An hydraulic system combining a motor; a reservoir; a first pumpof high capacity adapted to deliver oil to said motor to effect relatively rapid actuation thereof; a second pump adapted to be connected with the intake side of said motor to deliver oil thereinto, thereby to effect relatively slow actuation thereof; a third pump, receiving oil from said reservoir, adapted to have its discharge port connected with the exhaust side of said motor when the second pump is connected with the intake side of said motor thereby to maintain therein a pressure counter to the pressure built up in the intake side by said second pump; a high pressure relief line for said third pump; a low pressure relief line for said third pump; and a valve for connecting one of the first two mentioned pumps with said motor and for connecting said third pump with said low pressure relief line when the first pump is connected with the motor. 3. An hydraulic' system combining a motor; a reservoir; a first pump of yhigh ca-l pacity adapted to vdeliver oil to said motor to effect relatively rapid actuation thereof; a second pump of high pressure adapted to have its 'discharge port connected with the intake side` ofv said'motor to deliver oil therein to; a discharge conduit connected with the exhaust side of said motor and extending to said reservoir; a high pressure relief valve embodied in said conduit; a third Apump' of high pressure andlow capacity receiving oil from' said reservoir and connected with the exhaust side of said motor when4 the second pump is connected with the intake side of said motor, to build up back pressure therein; a second relief line for saidsthird pump; a

through said second relief line; a valve for selectively rendering either said first or sec-- ond pump effectiveto actuate said motor and lhave its discharge port connected with the intake side of said motor to deliverooil thereinto; a discharge conduit connected with the exhaust side of said motor and withthe intake port of said second pump; a third pump of high pressure receiving 011 from said reservoir and injecting it`into said discharge conduit; a yhigh pressure relief valve in said discharge conduit `to limit the maximum pressure therein; an auxiliary relief conduit adapted to be connected with said third pump; a low pressure relief valve embodied in said auxiliary relief conduit; and valve low pressure relief valve controlling the flow means selectively to render said first or second pumps effective to actuate said motor and to connect the third pump with said f auxiliary relief conduit when said first pump y5 is rendered effective.

5. An hydraulic system combining a motor; a rst pump adapted' to. deliverv oil. into said motor to effect rapid actuation thereof;` a second pump adapted to have its 16 intake aild discharge ports connected respectively with the opposite sides of said motor to effect slow actuation thereof; a third pump adapted to maintain a high pressure on the exhaust side'of said motor during slow actuation thereof; a high pressure relief valve connected with said third pump and determining thepressure in the exhaust side of said motor; a low pressure relief valve disconnected from said third pump during slow '26 actuation of said motor; and valve meansforsimultaneously connecting said first pump with said motor, short-circuiting said second pump, and connecting said low pres-v sure relief valve with said third pump. v 251 6. An hydraulic system combining a vmotor; a reservoir; a first pump of high-I 'capacity and relatively low pressure adapted to have its intake port connected with the exhaust end of said motor and its discharge port connected with the intake end thereof to effect rapid actuation of said motor; a hi h .pressure pump adapted to haveeitsinta e port connected with the exhaust end of said motor and its discharge port connected with the intake end thereofto. effect slow actuation of said motor; valve means selectively to rendersaid pumps effective to actuate said motor; 'a high pressure booster pump receiving oil from said reservoir, said booster pump 40 having its discharge yport permanently conl nected with the intake port of the first pump and temporarily connected with the exhaust end of said motor when the motor is actuated by said second pump; a high pressure relief valve permanently connected with the discharge line of said booster pump; and a low pressure relief line temporarily connected with the exhaust line-of said booster pump during rapid actuationof said motor 5U bysaid first pump.

In witness whereof, we have hereunto sub-r scribed our names. HANS ERNST. LESTER F. NENNINGER.

Images